Combination valve mechanism for hydraulic power systems



June 17, 1969 M. D. RoBlNsoN 3,450,007

COMBINATION VALVE MECHANISM FOR HYDRAULIC POWER SYSTEMS Filed Feb. G, 1967 fw@ *N Nh R.

June 17, 1969 M. D. ROBINSON 3,450,007 COMBINATION VALVE MECHANISM FOR HYDRAULIC POWER SYSTEMS Filed Feb. e. 196'/ sheet 2 ef 2 V] OPERATOR J6 BYPASS INVENTOR. Nome/5 D. Ro/Nso/v iinited States Patent O U.S. Cl. 91-445 9 Claims ABSTRACT OF THE DISCLOSURE Disclosed herein is a hydraulic (eg. lift) system embodying a reservoir, a continuously-operating pump, a hydraulic actuator linkage (e.g. cylinder), manual control and a hydraulic circuit including three -valves in an arrangement such that- (a) The output of the pump can be bypassed to the reservoir when there is no power demand,

(b) The pump output can be supplied to the actuator for power (e.g. lift) operation under manual control,

(c) The circuit will provide full, non-leaking containment of the hydraulic uid in the actuator so as to sustain a load that has been acted on in the power-operation of the actuator, without replenishing supply of uid from the pump, and

(d) There is provided an operating sequence in which the hydraulic uid can be released from the actuator.

The actuated apparatus may be a tailgate lift for a cargo truck and the like, in which a lift platform and its load are elevated to the level of the truck oor in the power-operation, and are sustained in the elevated position by the trapped uid, while the load is moved from the platform into the truck or vice versa.

Background f invention In the tailgate lift art, the commonly used powerlift apparatus includes a pump, a piston-cylinder actuator arranged to exert lift against a swinging lift-arm structure usually including a parallelogram arrangement for maintaining the lift platform levelled while elevating it, and control valve means for directing pressure uid into the actuator for lift operation, and for bleeding iiuid from the actuator 'for lowering operation. Since the valve employed for controlling such pressure iiuid delivering and releasing operations is one having inherent leakage, it has been considered necessary to provide mechanical latching means for holding the platform in its elevated position and preventing it from sagging during load-transfer operations.

In the prior patented art, Novotney 3,065,868 discloses a mechanical latch for securing the raised ends of the swinging arm structure to the truck bed to positively hold the lift mechanism in its elevated position, achieved by operation of a hydraulic cylinder under control of a multiposition valve which is shown in the patent. Lugash 3,269,567 discloses a mechanical lock operating between the fulcrumed end of the lift arm structure and its mount bar, for latching the lift mechanism in its elevated position. Wood 2,826,316 discloses a fluid actuator incorporating a pressure accumulator for maintaining pressure therein when its fluid circuit is de-energized.

Summa/y of invention The general object of the invention is to provide an improved combination of hydraulic actuator circuit, three valves and valve operating linkage operable by a single lever, in an arrangement such that movement of the lever in one direction (e.g. up for a lift operation) will powerenergize the actuator to act upon (e.g. elevate) a load;

wherein return of the lever to a neutral position will e'ect leakage-proof trapping of the fluid; and wherein movement of the lever to a limit position in the return direction will release the trapped fluid and thereby effect return movement of the load and actuator under the force exerted by the load. The valve combination includes a primary control valve having at least three positions; namely:

(l) A power position for routing pressure Huid to the actuator for moving the load,

(2) A neutral position in which the other two valves operate to close the line to the actuator when the load has reached an intended position, and for bypassing the pump output to reservoir; and

(3) A release position for routing return iiuid from the actuator back to reservoir when the load is to be released or returned to its starting position, the control valve being operable with a metering action during such return operation.

The combination includes a second valve (a check valve) which conducts flow from the pump to the actuator but blocks return flow so as to provide non-leaking entrapment of the fluid in the actuator, thereby sustaining the load (e.g. against sagging of a loaded lift platform). The combination further includes a return-control twoway valve, manually operated in lost-motion relation to the primary control valve, to an open position for bypassing the return flow of trapped fluid past the check valve so as to release the load, and to a closed position in which it cooperates with the check valve to trap the uid in the actuator. The general object of the invention is to provide such a combination of valves with manual operating linkage having a lost-motion connection or connections to one or both manually operated valves, in a hydraulic pump and actuator system in which the operative linkage is selectively operable to direct pressure fluid into the actuator, to trap the uid in the actuator, and to release the iluid from the actuator.

A more specific object is to provide such a system which is especially suitable as embodied in a tailgate lift wherein a loaded platform is sustained by the actuator in a non-sagging manner in an elevated position, without the use of latching or other mechanical support means.

A further object is to provide such a system wherein there is provision for constant operation of the pump, with bypassing of fluid from the pump to reservoir when the pump output is not being applied to the actuator to move the load.

These and other objects will become apparent in the ensuing description and appended drawing, in which:

FIG. 1 is a view of the valve and manual operating means, with parts of the valves shown in section and other parts of the system schematically shown; and

FIGS. 2, 3 and 4 are schematic disclosures of lift, neutral and release positions respectively of the main control valve; and

FIG. 5 is a schematic diagram of a system providing two-way power operation of the actuator instead of utilizing gravity for return operation.

Description of invention Referring now to the ydrawing in detail, I have shown therein, as an example of one form of apparatus in which the invention may be embodied, a hydraulic lift system for a tailgate apparatus comprising, in general a platform P carried by the vertically swingable end of a parallel arm lift linkage L pivotally fulcrumed at its other end upon a mount M attached to the underside of a truck bed or the like B and power-lifted by a cylinder type actuator A so as to elevate platform P from a loading position (shown in phantom) adjacent ground level G t0 an elevated position (full lines) in which it is leveled with the floor of truck bed B. Control of the actuator A is provided by a combination of three valves, namely a primary control valve V1 which, for example, may be in the form of a slidable spool valve, a unio-w check valve V2 shown, by way of example, in the form of a ball valve, and a return-control valve V3 shown, by way of example, in the forr'n of a rotary valve such as a ball cock. Valves V1 and V3 are connected, by lost-motion control linkage C, to a manual operator handle D. Valves V2 and V3 cooperate to trap'uid in actuator A at the end of a lift operation.

The system further includes a hydraulic system shown schematically and comprising, in general, a` pump P arranged to draw hydraulic fluid from a reservoir R and to direct it to actuator A through primary control valve V1 and check valve V2, and to bypass its output directly back to reservoir R through valve V1 when the latter is adjusted to a neutral position cutting off the delivery of pressure fluid to the actuator A. Thus the pump can continue to operate in an unloaded condition while the actuator is locked in a load-sustaining condition.

'In detail, the valves V1 and V3 may be mounted on a common base adapted to be secured to truck bed B in a suitable position. Valve V1, being a multi-position valve, is preferably a spool valve embodying a cylinder 11 and a piston 12 slidable axially therein between the several positions shown in FIGS. 2, 3 and 4. Cylinder 11 has an inlet 13 to receive pressure fluid from pump P through a fluid line 16, an outlet 14 to deliver the pressure fiuid to valves V2 and V3 through a fluid line 17, and an outlet 15 to release fluid into a return line 18 for return iiow to reservoir R. Piston 12 is a cylindrical bar, with a plurality of cylindrical portions fitted closely in a bore in cylinder 11, including end portions carrying respective O-rings 19 for sealing the respective ends of the cylinder, and several axially spaced annular lands including those shown at 21 and 22 in FIGS. 2-4. Valve V1 may be a conventional spool valve, and is shown in simplified form with only enough detail to illustrate its operative relation to the reminder of the apparatus. Between the lands 21 and 22 and adjacent portions of piston 12, annular valve chambers 23, 24 and 215 are defined within the bore of cylinder 1'1. The bore of cylinder 11 is defined by a plurality of annular lands 51 which are axially spaced at substantially equal intervals to define a plurality of annular passages, including those numbered 52, 53, 54 and 55. Piston land 221 is wider than passages A52-55 so as to block a passage when centered across the same. Piston land 22 is narrrower than passages 52 55 so that fluid may flow past land 22 through any passage 52-55 over which land 22 may be centered. Pressure ,inlet `13 is a port having branch passages communicating with annular passages 53 and 55 respectively. Annular passage 52 communicates with actuator-connected port 14. Annular passages 53 and 55 straddle the return outlet port 15, which communicates with the intermediate annular passage 54.

'In the power-transmitting position of valve V1 shown in EIG. 2 (for lifting operation of actuator A) pressurized fluid from pump line 16 is transferred from inlet port 13 to actuator outlet 14 through Ichamber 23 as indicated by the flow arrows, while return port `15 is closed od by lands 21 and 22. Thus fluid pressure is applied to actuator A. In the bypass (neutral) position of FIG. 3, actuator outlet 14 is closed by land 211, interrupting the ow 0f pressure uid to actuator A, and the pump output is bypassed from inlet port 13 to return outlet port 1-5 through valve chambers 24 and 25 as indicated by the iiow arrows, thus permitting pump P to continue operating in an unloaded condition, while fluid is trapped in actuator A (where the neutral position follows a power stage) as explained hereinafter. In this position, the narrow piston land 22 is disposed over the wider annular cylinder passage 54, and one or both of the annular valve chambers 24, 25 are in communication with passage 54, which conducts the fluid to the return outlet 15. In the release position of FIG. 4' following a major shifting movement of piston 12, actuator port 14 and inlet port 13 are both connected to return outlet 15 by valve chamber 25, thus `continuing the bypassing of the pump output to reservoir yR Iwhile simultaneously effecting the release of fluid from actuator A through valve V3 as hereinafter explained. ln this valve position, narrow piston land 22 is substantially centered over'annular passage 53, Iwhich establishes communication between annular chambers 24 and 25, as indicated by the ow arrows, and one branch of inlet '13 is in communication through annular passage `53 with annular chamber 25, which in turn is in communication with return outletrlS.

At this point, it may be noted that the succession of positions shown in FIGS. 2, 3, and 4, in that order, are attained by successive shiftings of the valve piston 12 in one direction (leftward as viewed in the drawing) from power to bypass and then to release position. Inversely, reading upwardly from BIG. 4 to FIG. 2, movement'of val-ve piston i12 in the opposite direction from its release position to its power position will effect lift operation, and may be executed with or without a stop at the bypass position.

Valve V2 is a check valve and may be of conventional ball type as indicated. It is arranged in a line 26 providing a bypass between line 17 and a connecting fluid line 28 leading to actuator A. A T-connection 29 provides parallel connections between line 17 and valves V2 and V3. Valve V3 is a two-position valve of a type providing a complete hydraulic seal in a closed position (shown in full lines) and operative, in an open position, (shown in phantom) to conduct return tlow from actuator A through fluid line 28 to line 17, thence to primary control valve V1. Valve V3 may suitably be a cock valve of a type having effective hydraulic seals for sealing its rotor 31 to its case 32. The details, being conventional, are not shown. Rotor 31 is attached to an operating arm 33 (broken away so that rotor 31 and surrounding portion of case 32 may be shown in section) for rocking the rotor from the closed position shown, to its open position in which fluid may flow from actuator A through the valve V1 in its release position (FIG. 4) to return line 18 and thence to reservoir R.

Valve V1 has an operating arm 35 pivotally fulcrumed at 36 at one end to a foot of valve cylinder 11 and pivotally linked at 37 to the adjacent end of piston 12.

Operating linkage C includes a lost-motion link 40 having in one end a longitudinal slot 41 pierced by a transverse pin 42 on the other end of valve arm 3S, and having its other end pivotally linked at 43 to a crank arm 44 on a crank shaft 45. Crank shaft 45 is journalled in bracket bearing means 46, 56 secured to or part of valve base 10. Operator handle D also is secured Ito or part of crank shaft 45 and is operable to rock the arms 44 and 35 from the neutral (bypass) position shown in full lines and designated 2 to the following positions shown in phantom and designated by the following numerals: 1 lift operation; 3 release for lowering operation. Corresponding positions of link 40 and valve arms 33, 35 are similarly designated 1, l2 and 3. Lost motion operation of link 40 on arms 33, 35 involves additional, intermediate positions of these parts, attained in the shift from release to power position, and which are designated 4. The bypass position 2 of arm 35, arrived at in the shift from power position back toward release position, is substantially the same as its bypass position arrived at in the return shift from release position toward power position. Link 40 has in its intermediate portion a notch 46 through which extends a transverse pin 47 in the end of valve arm 33.

, Notch 46 has respective ends defined by shoulders 48 and 49. Shoulder 49 is adapted to engage pin 47 during motion of link 40 in the direction to effect lift operation (indicated by the legend up and its associated arrow). Such engagement is established in an early stage of this stroke of link 40, to close valve V3 for trapping hydraulic fluid in actuator A. Contact is made with pin 47 in the leftward position thereof (phantom). The closing of valve V3 is completed at the intermediate position 4, Ilink 40 then being in its position 4 also. During continued movement of link 40 to its final position 1, valve V3 will remain closed while overtravelling from its position 4 to its position 1 shown in full lines.

During movement of link 40 in the DOWN direction, shoulder 48 will engage pin 47 for opening valve V3 and thus releasing the trapped fluid from an actuator A, so that the platform P and its associated load may descend by gravity from elevated to lowered positions, causing the fluid to be returned from the actuator to reservoir R.

Operation The operation of the apparatus will be described in terms of the tailgate lift disclosed in the drawing, wherein the weight of platform P and its load, plus the weight of parallel-arm linkage L, is effective to return to the piston of actuator L to the lower limit of its stroke, releasing from the lower end of the actuator cylinder the hydraulic fluid which has been forced into said lower end by pump P in the lift stage of operation although it will be understood that other mechanisms employing a hydraulic actuator to act upon a load which is operative to drive the fluid from the actuator -in a return stage of operation, may also incorporate the invention.

Starting with the platform in the elevated position shown in full lines, as soon as the platform has reached that position the operator will normally return the operator handle D from the up position 1 back to the neutral position 2, thereby causing link 40 at the end of slot 41 t0 engage follower pin 42 af-ter some lost motion, so as to move valve V1 a short distance. The parts will then be in the positions shown in full lines in the drawing, valve V1 being adjusted to the bypass position of FIG. 3 so that the pump may continue to operate in an unloaded condition, and previously closed valve V3 remaining closed so as to trap the fluid in actuator A, thereby to sustain the load in the elevated position. When the platform is to be lowered, the handle D is again moved, in the same direction, from the neutral position 2 to the down position 3, thereby moving valve V1 to its release position of FIG. 4. During this movement, after an initial stage of lost motion, shoulder 48 will engage pin 47 of valve V3 and as the movement is completed, valve V3 will be shifted to its open position 3. After valve V3 is partially opened, valve V1 will operate with a metering action as it approaches its FIG. 4 release position, thus providing maximum neness of control in lowering platform P against the ground without shock. When this is attained, the operator may optionally return handle D to its neutral position, or may do so as part of a continuous movement of the handle from its down position 3 to its upward limit position. During this movement link shoulder 49 will approach pin 47 of valve V3, but will not engage it, and valve V3 will thus remain in its release position 3. Also during the initial stage of this movement, arrn 35 of valve V1 will remain stationary with its pin 42 sliding in slot 41 and as link 40 approaches its neutral position 2, arm 35 will be engaged at the intermediate position designated 4.

To effect lift operation, the handle D is shifted so as to move link 40 to its limit position 1. Shortly after the handle leaves its neutral 2 its shoulder 49 will engage pin 47 to effect the return of valve V3 toward its intermediate closed position shown in phantom at 4. Being of the rotory cock type, valve rotor l31 can rotate beyond this initially closed position to its limit closed position shown in full lines corresponding to the 1 position of link 40, in order to permit the further movement of link 40 to move valve V1 to its power transmitting position (arm 33 advancing to its limit 1 position). In moving the operating lever yD upwardly its upper limit position can be determined by engagement of suitable stop means associated with lever D, arm 44 or valve arm 33;. Valve V1 will thus be adjusted to its power position (FIG. 2) and will direct fluid into actuator A through check valve V2, which will open to pass the fluid through line 26.

FIG. 5 illustrates, in schematic diagram form, how the invention can be adapted to a hydraulic system utilizing a two-way operable actuator instead of the gravityreturned actuator described above. Such a system may be one in which it may be necessary to move the load in both directions by actuator operation. instead of the single fluid connection to actuator A shown in FIG. l, a second fluid line 28A may provide a connection between a fourth port of valve V1 to the end of actuator A opposite the end to which line 28 supplies fluid. The spool valve illustrated is of a conventional type commonly having a second fluid outlet port 14, shown only in FIG. 5, to which line 28A is connected. Release of fluid from actuator A through valve V2 will provide for return flow from the opposite end of actuator A when its one end is receiving fluid under pressure through line 28A. When pressurized fluid is being delivered through line 2-8, the operation is the same as in FIG. 1, and similar reference numerals are used to designate the corresponding parts of the two systems.

I claim:

1. In a hydraulic system including a hydraulic actuator and a pump for supplying hydraulic fluid thereto, the improvement comprising, in combination:

a primary control valve having an inlet connected to the pump to receive its output, an actuator port for transfer of fluid between the valve and said actuator, and a return outlet for discharging fluid to the inlet side of Said pump;

a connecting fluid line communicating with said actuator port at one end and with said actuator at its other end, said connecting line including parallel branches;

a check valve in one of said branches, operable in response to fluid pressure to transmit a full range of actuator-operating flows of pressure fluid from said control valve to said actuator so as to provide an actuating body of hydraulic fluid therein and to block return flow from said actuator to said control valve;

a return flow valve in the other of said branches, operable when open to transmit return flow from said actuator to said control valve, and cooperable with said check valve when closed to trap the actuating body of hydraulic fluid in said actuator for holding a load;

and val-ve operating means linking said return and control valves, said last means being operable in an actuator-energizing stage to close said return flow valve and to actuate said lcontrol valve to a power position in which it will connect its inlet to its actuator port so as to direct fluid under pressure through said connecting line and said check valve to said actuator, and operable directly on said return flow valve in a return stage of operation to open said return flow valve without affecting said check valve for release of the trapped fluid from said actuator and to move said control valve to a position in which it connects said actuator line to said return outlet for conducting the return flow back to the pump.

2. The system defined in claim 1, wherein said operating means is associated with said control and return flow valves in a manner to effect closing of said return flow valve before completing the connection of the inlet port to the actuator port of said control valve for directing pressure fluid into said connecting line, said control valve having a metering action in completing said connection.

3. The system defined in claim 2, wherein said return flow valve is a rotary cock valve adapted for overtravel to accommodate movement of said operating means from the position of initial closing of said return valve to the position of advance of said control valve to its said power position.

4.' The system defined in calim 1, wherein said operating means includes a lost-motion connection between said control and return valves such as to delay the actuation of the control valve relative to that of the return valve during the said actuator-energizing stage, and vice versa in said return stage of operation.

5. The system defined in claim 1 including a reservoir on said inlet side of the pump and feeding the same, said return outlet being connected to said reservoir to return fluid thereto.

p 6. A hydraulic system as defined in claim 1, in combination with a tailgate lift apparatus including a platform and lift linkage connecting said platform to a support for elevating and lowering movement, said actuator being connected between said support and said lift linkage for elevating said platform while supporting a load thereon.

7. A hydraulic system as dened in claim 1, wherein sai-d operating means comprises respective actuator arms conencted to said return valve and to said control valve for shitting their valving positions when rocked;

an operator crank; and

a link connected thereto for longitudinal movement in response to rocking of said crank, said link including a lost-motion connection with said return valve actuator arm such as to provide for return of said crank to a neutral position following the completion of an actuator-energizing stage, while leaving said return valve in a closed position to maintain fluid trapped in said actuator for load-sustaining, until said crank is advanced to a return-How position.

8. A hydraulic system as dened in claim 1, wherein said operating means comprises respective actuator arms connected to said return valve and to said control valve for shifting their valving positions when'rocked;

an operator crank; and

a link connected thereto for longitudinal movement in response to rocking of said crank, said link including a lost-motion connection with said return valve actuator arm such as to provide for return of said crank to a neutral position following the completion of an actuator-energzing stage, while leaving said return valve in a closed position to maintain uid trapped in said actuator for load-sustaining, until said crank is advanced to a return-How position; said control valve having means to bypass the pump output back to the inlet side of the pump when said crank isA adjusted to said 'neutral position.

9. A hydraulic system as defined in claim 1, wherein said control valve includes means to bypass the pump out# put back to the inlet side of the pump in a neutral posi' tion of said operating means, whereby to unload the pump when tiuid is not :being delivered to the actuator.

References Cited UNITED STATES PATENTS 1,855,060 4/ 1932 Landenberger 91-445 3,060,898 10/1962 Ritter 91-447 3,088,283 5/1963 Furia 91-447 3,307,455 3/1967 Peras 91-450 `CARROLL B. DORITY, I R., Primary Examiner.

U.S. Cl. XR. 91--447 

